Combining a page map with a PDF so that annotations move with pages in updated PDFs

Question

Has anyone managed to provide an end-user with an updated PDF, allowing that user to transfer his local annotations to the new PDF and keeping the annotations on the correct page, even when there are pages inserted into the update PDF at a point earlier in the PDF than the annotations.

I thought there might be a page map or page guid approach that someone has used.

Sorry - I hope that is clear.

Answer 1

Instead of using the page index as ID of the page, you can use the page content stream instead (after decoding/decompression). Most PDF libraries will give you access to that, so you could compute an MD5 hash from the page content and search for that instead on your "updated" file in order to know where to transfer your annotations.

This is assuming that the page content will be indeed identical, which is not a common scenario.